Automatically reversing, double acting fluid cylinder mechanism

ABSTRACT

A double acting fluid cylinder and piston unit having valve control means for providing constant reciprocating motion of the piston. The valve control means includes a pilot spool which is actuated by the piston at either end of its predetermined travel, and which spool then directs pressure fluid to actuate a flow directing spool so that pressure fluid is directed to the opposite end of the cylinder to thereby reverse direction of movement of the piston. The relationship between the pilot spool and follower means on the piston is externally adjustable to vary the stroke of the piston.

Unite States atent 1 Landherr et al.

[ 1Ma1rch 13, 1973 1 AUTOMATICALLY REVERSING,

DOUBLE ACTING FLUID CYLINDER MECHANISM [75] Inventors: Lawrence R.Landherr, Racine; Karl J. Prohaska, Pewaukee, both of Wis.

[7 3] Assignee: Milwaukee Cylinder Corporation [22] Filed: May 24, 1971[21] Appl. No.: 146,407

FOREIGN PATENTS OR APPLICATIONS Primary ExaminerPaul E. MaslouskyAtt0rney.lames E. Nilles [57] ABSTRACT A double acting fluid cylinderand piston unit having valve control means for providing constantreciprocating motion of the piston. The valve control means includes apilot spool which is actuated by the piston at either end of itspredetermined travel, and which spool then directs pressure fluid toactuate a flow directing spool so that pressure fluid is directed to theopposite end of the cylinder to thereby reverse direction of movement ofthe piston. The relationship between the pilot spool and follower meanson the piston is externally adjustable to vary the stroke of the piston.

1 Claim, 5 Drawing Figures PATENTEDHAR 1 31975 sum 2 or 2 AUTOMATICALLYREVERSING, DOUBLE ACTING FLUID CYLINDER MECHANISM BACKGROUND OF THEINVENTION The invention pertains to double acting hydraulic and pistonunits wherein movement of the piston to the end of its travel in onedirection acts to shift a control valve to thereby cause the piston toreverse its direction of travel. Upon reversing its direction of travelin the opposite direction, the valve mechanism then again acts toreverse the travel of the piston in the opposite direction.

Devices of this character have been proposed heretofore, but havegenerally been expensive to manufacture because of their complicateddesign which usually involved numerous four-way and three-way valves incombination. Furthermore, these prior art devices required that thedevices travelled through its entire stroke before changing directions,and were difflcult or impossible to adjust as to the length of pistonstroke.

SUMMARY OF'TI-IE INVENTION The present invention provides a fluidoperated, double acting cylinder and piston power unit, the piston ofwhich is automatically reversing in its direction of travel, and thelength of travel of the piston can be readily changed by externaladjustment. The device utilizes a minimum number of parts in its controlmechanism, is simple in operation, easy to adjust and maintain, andrequires only one pressure fluid input. Easily adjustable and positivelylocking collars are provided for external access, and efficient andreadily replaced bushings are also provided for the control spool of thecontrol mechanism.

These and other objects and advantages of the present invention willappear hereinafter as this disclosure progresses, reference being had tothe accompanying drawings.

BRIEF DESCRIPTION OF TI IEDRAWINGS FIG. 4 is an enlarged, fragmentarycross sectional view of the bushing shown in FIG. 3; and

FIG. is an enlarged, perspective view of the locking collar shown inFIGS. l, 2 and 3.

DESCRIPTION OF A PREFERRED EMBODIMENT A cylinder unit U which is shownfor purposes of illustrating the invention is shown as having a piston 1with piston rods 2 and 3 extending therefrom, one for each side of thepiston. However, the invention is equally applicable to pistons having asingle rod. In any event, he piston is slideable within the cylinderchamber 4 of the conventional cylinder 5. The ends of the rods 2 and 3have clevises 6 and 7, respectively, or other attaching devices, bymeans of which the piston can be attached to the parts to be shifted.

The valve assembly VA includes a housing 10 which is rigidly secured toone end of the cylinder. A pilot spool 11 is slideably located in bore12 in the housing and its ends 110 and 11b are extendible from oppositesides of the housing. This spool has a hole 11c extending entirelytherethrough and furthermore has lands 11d, lie, and lllf formed thereonto define annular grooves 11g and 11h located between the lands. Thespool is slideably sealed with the housing by means of the combinationend plug and seal bushings l3 and 13' which are threaded into thehousing 10 so that O-rin'gs 13a are compressed by shoulder 13b of thebushing. Packing 13c (FIG. 4) and another O-ring seal 13d are alsocarried by the bushing.

A threaded rod slideably extends through the hole 11c of the spool 11and has positionable clamp-type, lockably threaded collars 21 and 22threaded thereon. The collars can be locked along the rod by the screw23 extending through the split in the collar. Thus the collars areadjustable along the rod to any position so as to determine the strokeof the piston, as will appear. When the collars 21 and 22 engage therespective ends of the spool 11, they shift the spool in the appropriatedirection, as will appear. The rod 20 is secured to one end of thepiston for movement with the piston by means of the bracket 25 which isfixed to the piston by set screws 26 and fixed to the rod by the nuts27.

A directional spool is slideably mounted in bore 41 in the housing, theends of the bore 41 being closed by the plugs 42 and 43. Spool 40 haslands 41a, 41b, 41c which define annular grooves 41d and 41a.

Various fluid passages interconnect the two spools '11 and 40 and alsoconnect the opposite ends of the cylinder 5, as follows. A generallycentrally located, pressure fluid supply passage receives pressure underfluid from line 51 and pump 52. Passage 50 is in communication with bothspool bore 12 and 41.

When the pilot spool 11 is in the position shown in FIG. 1, pressurefluid is directed from supply passage 50 through the annular groove 11bof spool 11, and then via pilot passage 52 to one end of the bore All.

When the fluid is directed via pilot passage 52 to the first end of bore41 in the valve assembly, it acts to shift the directional spool 40 tothe left as shown in FIG. 1, thereby permitting pressure fluid from line50 to also pass through the annular grooves 41e of valve spool 40 andthen through a passageway 55 and into one end of the cylinder 5, therebycausing the piston l to move to the right from its left hand positionshown in FIG. 1. At the same time, fluid from the opposite end of thecylinder 5 is returned via fluid line 57 which is in communication withsaid end of the cylinder, and then through passageways 58 and 59 andoutlet 60 in the valve housing, to the return line 61.

After the piston I has then moved to the right hand position shown inFIG. 2, and shifted spool 11 to the right, pressure fluid is cut offfrom pilot passage 52 and is instead being directed from passage 50 tothe pilot passage 54 and to the opposite end of the directional spool40. This causes the directional spool 40 to shift to the right, therebypermitting the pressure fluid from the supply passage 50 to also passthrough groove 41d of spool 40, passageway 58 of the valve assembly andthrough line 57 to the opposite end 62 of the cylinder 5. Fluid from theother end of cylinder 5 is returned via passageway 55, spool groove 41c,outlet 60 to the sump line 61. Pressurization of the end 62 of thecylinder then forces the piston 1 to move to the left until the collar21 abuts against the outwardly extending end 11a of the spool 1 lthereby causing the spool 11 to again shift to the left. Thereupon, thecycle repeats itself.

The collars 21, 22 are easily adjustable to and positively lock in theirposition along the rod to determine the length of stroke of the piston.This adjustment is infinite along the length of the rod and can easily,quickly, and accurately adjust the stroke of the piston.

By means of the present invention, an automatically reversing cylinderunit is provided which employs a valve assembly utilizing a minimumnumber of spools and which can be easily adjusted as to its stroke.

We claim:

1. Automatically reversing, double acting cylinder and piston mechanismcomprising, a cylinder, a piston reciprocable in said cylinder, ahousing attached to said cylinder, a first bore in said housing, ahollow tubular pilot spool slideable in said bore in said housing, abushing in each end of said bore of said housing, the ends of said pilotspool being positioned to slide through said bushings, sealing meanscarried by said bushings for slideable and sealing engagement with theoutwardly extending ends of said pilot spool, a

threaded rod extending through said pilot spool for slideable movementtherein and being connected with said piston for movement therewith, anadjustable locking collar located on said rod on each side of said valvehousing for abutment with said pilot spool exteriorally of said housingto cause shifting of said spool in said housing in one direction or theother, a second bore in said housing, a directional spool slideablymounted in said second bore in said housing, a pressure fluid supplypassage in said housing and in communication with each of said housingbores, pilot passages in said housing and placing said pilot spool borein communication with opposite ends of said directional valve bore,passageway means in said housing and communicable (l) with opposite endsof said cylinder, (2) with said directional spool bore and (3) with saidsupply passage when said directional valve is shifted in oppositepositions, and return passageway means in said housing in fluidcommunication with each end of said pilot spool bore, whereby when saidpiston moves to one extreme position or the other, said collars shiftsaid pilot spool and consequently shift said directional spool to causepressure fluid to reverse movement of the piston.

1. Automatically reversing, double acting cylinder and piston mechanismcomprising, a cylinder, a piston reciprocable in said cylinder, ahousing attached to said cylinder, a first bore in said housing, ahollow tubular pilot spool slideable in said bore in said housing, abushing in each end of said bore of said housing, the ends of said pilotspool being positioned to slide through said bushings, sealing meanscarried by said bushings for slideable and sealing engagement with theoutwardly extending ends of said pilot spool, a threaded rod extendingthrough said pilot spool for slideable movement therein and beingconnected with said piston for movement therewith, an adjustable lockingcollar located on said rod on each side of said valve housing forabutment with said pilot spool exteriorally of said housing to causeshifting of said spool in said housing in one direction or the other, asecond bore in said housing, a directional spool slideably mounted insaid second bore in said housing, a pressure fluid supply passage insaid housing and in communication with each of said housing bores, pilotpassages in said housing and placing said pilot spool bore incommunication with opposite ends of said directional valve bore,passageway means in said housing and communicable (1) with opposite endsof said cylinder, (2) with said directional spool bore and (3) with saidsupply passage when said directional valve is shifted in oppositepositions, and return passageway means in said housing in fluidcommunication with each end of said pilot spool bore, whereby when saidpiston moves to one extreme position or the other, said collars shiftsaid pilot spool and consequently shift said directional spool to causepressure fluid to reverse movement of the piston.